An optimal control model of a neuromuscular system in human arm movements and its control characteristics

Abstract

The joint torque which sets human limbs into motion is generated by a separate group of muscles provided for each joint. As the activation of each muscle is determined by a neural input, a neuromuscular system controlling all muscles has to be considered in order to understand human movements. In this study, an optimal control model of a neuromuscular system is investigated, and its control characteristics are examined. First, the dynamic and mechanical properties of a muscle are examined, and a neuromuscular system is formulated mathematically. Second, a performance criterion for the optimal control model is defined in order to characterize the dynamic behavior of the neuromuscular system, and a mathematical procedure for producing optimal trajectories is represented. Third, optimal trajectories in human arm movements are produced under various conditions of movement, and these trajectories are compared with experimentally observed ones. It is then verified that the optimal trajectories demonstrate human arm movements well. Finally, the behavior of individual muscles in various movements is examined quantitatively by means of simulation results, and the control characteristics of the human neuromuscular system are investigated.

Key words

Neuromuscular system Human arm movement Optimal trajectory

This work was presented in part at the Sixth International Symposium on Artificial Life and Robotics, Tokyo, January 15–17, 2001.